Current disk systems are generally designed to reduce read traffic more effectively. Hence, write traffic of the I/O workload could potentially become a bottleneck of the disk system performance. In order to overcome this problem without much cost, this paper presents using outermost-zone track of multi-zoned recording disk as a secondary disk cache. The proposed disk cache improves the disk system performance by following exploitations: speed difference between block transfer and track transfer, difference in transfer rate between outermost-zone tracks and inner tracks, reduction in the seek time caused by decreasing the number of disk cache tracks, and idle period during burst accesses. In addition, it does not waste the disk space because it allocates the caching space by the cylinder unit. The simulation results show that the proposed system improves 2.54∼3.11 times better in terms of average response time for write operations than existing disk systems..